He tried his hand at various trades, including gold mining, eventually settling in California, where he became engaged in the mercantile business.

He eventually worked for Hackfield & Co. in Honolulu, and then Thomas Spencer, and became successful with his own import and export business in the kingdom.

[1] King Kalākaua appointed him Minister of Finance on November 7, 1874, during which he was a member of the House of Nobles in the legislature.

[3] Within the next month, Walker publicly released "Statement of the Revenues and Expenditures of the Hawaiian Kingdom for eighteen years.

Along with Zephaniah Swift Spalding, Walker and Irwin organized William G. Irwin & Co.[5] In 1890, Kalākaua once again named him Minister of Finance, as well as ad interim Attorney General until William Nevins Armstrong accepted the position.